int strStr(char * haystack, char * needle){
    int len1 = strlen(haystack),len2 = strlen(needle);
    if(len2 == 0)  return 0;
    for(int i = 0;i < len1;i++)
    {
        int j = 0;
        if(len2 > len1-i) return -1;
        while(haystack[i+j] == needle[j++])
            if(j == len2) return i;
    }
    return -1;
}
